I have perfect pitch (or as it is more properly called, absolute pitch). To be honest, I am doubtful that these teach-your-kids-perfect-pitch techniques are effective: I don't think there's much evidence that they are, beyond anecdote.
Perfect pitch is more a parlor trick than anything. Sure, it's impressive, and I wouldn't trade it away. But the most important skill that a musician can develop (and any musician can develop it) is good relative pitch, that is, the ability to identify notes once told a baseline note. But people with perfect pitch are usually terrible at relative pitch.
For example, I was in a sightsinging class long ago, with one other student with perfect pitch. Sightsinging is a course designed to develop relative pitch. The professor would play a note, say, C, tell us it's a C, then proceed to play a series of chords. The relative pitch students would work out the chords based on the C. I and the other perfect pitch student would just write out the notes we heard. The professor got angry about this, so he started starting with a C but telling everyone it was, say, an F#. Then he'd play chords relative to the C and everyone but us two would write them all out relative to F#. The perfect pitch students were totally hosed, desperately trying to transpose the notes in real-time, with our brains constantly telling us that they're all wrong, and because our relative pitch was so bad as we had relied on perfect pitch as a crutch.
This also shows up in jazz. I'm a Jazz pianist and the thing I can't do is transpose in real time. That's a CRUCIAL ABILITY for a Jazz musician. But I can't do it because my perfect pitch keeps telling me the notes I'm reading are not the same that I'm hearing.
When I occasionally visited my parent's church services, the organist, who knew I had perfect pitch, would see me and immediately transpose the organ down by one half step with a dial. I then wouldn't be able to sing anything -- all the notes in the book were wrong. I'd look up and see him grinning at me. He knew that I knew, it was just between us two. He had screwed me over.
Starting around 50 years old, my pitch has started going sharp. This is a very common effect of age in people with perfect pitch. It depends on the instrument: sawtooth waveshape instruments (guitars, violins, harmonicas) are much worse than others. I'd hear a guitar at B and it sounds like a C.
It is hard to explain how disturbing this is. All your life you could recognize colors. People around you, who only saw in monochrome, would show you a blue object and you'd say "that's blue". This amazed them, but to you it just looks blue. But then one day someone shows you an object that looks blue, but it's not. It's green. The green meter confirms it. But it LOOKS BLUE. You can't explain why this is so disturbing because to everyone else it just looks gray. This effect has a strong psychological impact too -- I've seen interesting studies on it -- because the ego has been wrapped up tightly with your perfect pitch, and now it's failing, like a piece of you going wrong.